Pressure control system for blower-fed two-cycle engines



April 24, 1934. A. FIELDEN 1,955,799

PRESSURE CONTROL SYSTEM FOR BLOWER FED TWO-CYCLE ENGINES Filed Aug 24. 19:51

Patented Apr. 24, 1934 PRESSURE CONTROL SYSTEM, FOR BLOWER-FED 'rwo-cYcLE ENGINES Arthur Fielden, Detroit, Micln, assignor to (ion eral Motors Corporation, Detroit, Mich., a corporation of Delaware Application August 24, 1931,- Serial No. 559,009

6 Claims.

This invention relates to internal combustion engines and particularly to engines operating on the two-cycle order. It is further concerned with an improvement in the mechanism for supplying and for controlling the supply of carbureted mix- .ture to such an engine. Like other known engines it makes use of a blower to receive the mixture from the carburetor and deliver it to the engine manifold, a manually operable throttle valve being used between the discharge of the blower and the engine cylinder or the manifold in the case of a multi-cylinder engine. As in earlier forms the blower is particularly useful in that it delivers the charge without such pressure fluctuations as would disturb the so called strati-form condition of the incoming mixture and the burned gases. The variation in the work to be done is accomplished, as in prior inventions, by varying the pressure within the manifold, and this is attained by the manipulation of the throttle valve located beyond the outletof the blower. Such pressure variations are gradual and do not interfere with the strati-form condition referred to. Then, too, the partially closed throttle valve smooths out the pulsations from the blower. With the throttle wide open the pulsations become negligible.

With such an engine it has been found neces sary to not only control the manifold pressure by the throttle valve but to associate therewith automatic mechanism to similarly control the action of the blower in delivering mixture to the engine. The necessity for such automatic mechanism has arisen because it is not practical to employ a blower of such capacity or to drive it at such speeds as to maintain an approximately constant pressure on the blower side of the throttle valve for all loads on and speeds of the engine for the reason that such a blower would involve excessi e pumping losses. Itis therefore preferred to use a blower, the operation of which consumes but a'comparatively small part of the energy developed by the engine, and to work sucha blower harder when delivering relatively greater charges and less hard when delivering lesser charges.

It is, then, anobject of my invention to provide an improved automatic control of the output of the blower to the engine whereby the blower works relatively harder when delivering its maximum charge, and whereby its work is lessened when there is a lesser load on the engine. Other objects and advantages will be understood from the following description. I Y

The invention is illustrated in the accompanying drawing in which- 1 Fig. 1 is a view in side elevation partly in section. I

Fig. 2 is a vertical section through the blower" and control mechanism.

Fig. 3 is a section substantially at right angles to Fig. 2. Referring by reference characters to the draw- -ing, numeral 5 isused to designate one of the cylinders of the engine of the two-cycle variety,

the engine shown being of the V-t'ype. At '7 is the piston and 9 is the connecting rod for connecting the piston to the crankshaft 11. A head 13 isformed with a suitable combustion space 15 having leading thereto a passage 17 in the engine block, which passage is controlled by an inlet valve 19 actuated as usual by a spring 21 and a camshaft 23. At 25 is the conventional spark plug and 2'7 represents the exhaust openmg.

The induction mechanism is composed of three parts, a carburetor'29, a blower 31, and a control device 33. These parts are assembled relatively to each other and. to the engine as illustrated in Fig. 1.v The carburetor will, of course, be supplied with air and fuel as usual and the mixture is admitted to the blower chamber 35 through passage .37. The blower contains two rotors 39 gearedtogether as shown by gears 41 and driven by a chain 43 from the crank shaft. From the blower outlet 45 passages 4'7 communicate with the before-mentioned passages 17 in the engine block. The blower element 31 also has one or more bypasses 49 leading from spaced positions at the top of member 31 and communicating with the blower inlet 37. The control device 33 forms a cover closing an opening 51 in the blower member 31. An opening 53 in the base of this cover guides a circular throttle valve 55" which controls the flow of the mixture from the outlet 45 to the passages 47. 'The throttle valve has a stem 57 extending up through a cap 59 over the top of the control member 33. The stem is intended to be reciprocated by any preferred operating mechanism as shown. Surrounding the stem is a valve 61 with a tubular wall and a bottom closure 63. Valve 61 is concentric with valve 55 and its lower end is reduced to slidingly engage a notched portion 67- at the upper end of throttle valve 55. A spring 69 engages the base 63 of valve 61 and atits otherend engages an abutment 71 on the stem 57 of valve 55. A larger spring 73 also engages.

the base 63 and its upper end may be secured to the periphery of disc 75 on the lower end of a tubular rod 77 surrounding the stem 57. Above 4 the cap 59 a forked arm '79 is secured to the tubular rod 77 by fasteningmeans 81.. It will be seen that when the valve 61 is raised it affords communication from the outlet 45 of the blower to'theregion of the control member 33 around the valve from which cor'nmunication'is also provided through the bypassages 49 to. the entrance of the blower.

Bevel gear 83is secured to one of; the rotorin the control member 33.

shafts. It meshes with a mating bevel gear 85 carried on the end of a tubular shaft87. I This shaft 87 is rotatably mounted in a bearing 89. Above the top of bearing 89 the tubular shaft has an annular flange 91 spaced from the bearing 89 by a thrust bearing 93. The side walls of the tubular shaft are diametrically slotted as at 95 from the region of the flange 91 to the top portion 9'? into which top portion is threaded an end fitting 99. slidable through the opening of the tubular rod 87 isa solid rod 101 having a terminal disc 103 secured thereto. The disc 103 lies over the forks of arm 79 and the forks straddle the rod 101 as illustrated. The lower end of rod 101 carries a cross head 105 and a spring 107 surrounds the rod-101 and engages the head 99 of the tubular rod and the cross head 105 of the solid rod, thereby tending to hold the solid rod' 101 in its downward position. Links 108 are pivoted to the head 99 at 109. These links carry weights 111. At intermediate points 113 of the links 108 other links 115 are pivoted, which latter the influence of the governor when the parts.

thereof are as shown in Fig. 1.

There may also be used an auxiliary air device It comprises a valve 119 closing an opening 121 under the infiuenceof a spring 123, the valve being suitably guided by a rod 125 slidable in a boss 12'! formed preferably integrally with the part 33. Air entering at 121 communicates with the inlet to the blower by way of the bypass 49. The operation of the improved engine is substantially as follows:

When the throttle is set for idling the manifold pressure-is-low.. In this position of the throttle valve the pressure of spring '73 on the bypass valve, insofar as it is influenced by the position of the throttle valve, is compartively low. As a result the valve 61 is lifted by the pressure of the mixture from the blower output and most of this.

mixture passes through the passage 49 to the blower inlet. As the throttle valve is raised to open position it lifts the bypass valve with it. In

so doing the pressure of spring 69 is unchanged, but the pressure of spring '73 increases in proportion as the throttle valve is lifted, assuming its upper abutment te-remain stationary. With the throttle valve in open position the load on the bypass valve 61 becomes such that the mixture the disc 103 in or near the position shown in thedrawing where the disc engages the forked ends of arm '79 and in which position the abutment of spring '73 is depressed so that a considerable spring resistance is brought to bear against the bypass valve 61. If the engine starts to race as from a suddenly reduced load, the balls 111 rise and lift the disc 103, thereby permitting spring 73 to expand and reduce the load upon the bypass valve.

Under these circumstances a part of the mixture will traverse the bypass. gine is reduced and the racing stops. This-automatic direct. control of the spring load on the bypass valve is intended to accomplish the .results heretofore sought to be attained by a passage from the inlet manifold to the bypass inthe region of its valve,-wherebyv the pressure condition in said passage was used to influence the load on thebypass valve.

I claim:

1. In combination with an engine, a carburetor, a blower, a passage between the blower and engine, a manually operated throttle. valve in said passage, a bypass from the outlet of the blower to its inlet, a spring loaded valve -in said bypass, means associated with said valves whereby the The supply to theen load of said spring increases as the throttle valve opens, and governor means operated by said engine to decrease the load on said bypass valve as the speed of the engine increases.

2. The invention set forth in claim 1, said governor means comprising gearing associated with said blower mechanism, and mechanism con trolled by the governor constituting a variably positioned abutment for the bypass valve spring.-

3. The invention defined by claim 1, said governor means comprising gearing driven by the blower, a movably mounted abutment for the bypass valve spring, a rod connected to said abutment, an arm on said rod, said governor means also including weights and a spring and an ele-, ment actuated thereby to engage said arm and hold the bypass valve spring under relatively high compression when the engine is idling, whereby the load on the bypass valve is relieved as the engine speed increases.

4. In combination with an engine, a carburetor, a blower, a passage between the blower and engine, a manually operable throttle valve in said passage, a bypass from the outlet of the blower to the inlet, a spring-loaded valve in said bypass, the abutment of said spring being movably mounted, and governor means controlled by the speed of the engine to move said abutment whereby the spring load on the bypass valve is reduced when the engine speed increases whereby the fluid pressure may be enabled to open the bypass by overcoming the spring load on the bypass valve at high engine speeds.

5. In combination with an engine, a carburetor, a blower, a passage between the blower and engine, a manually operable throttle valve in said passage, a bypass from the outlet of the blower to the inlet, a spring-loaded valve in said bypass, the abutment of said spring being movably mounted, and governor means controlled by the speed of the engine to move said abutment where-' by the spring load on the bypass valve is reduced when the engine speed increases, said throttle valve contacting said bypass valve and movable therewith whereby said spring load on the bypass valve is increased as the throttle valve is opened.

6. In combination,- an engine having a blower, means forming a passage from the blower to the, engine, a throttle control in said passage, means forming a bypass from the outlet to the inlet of the blower, a valve in said bypass, means to variably load said valve, said means being responsive to throttle position and engine speed.

ARTHUR FIELDEN. 

